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{\bf {\sc OP-01} \hspace{0.3cm} Dynamic fluorescence imaging of direct HIV-1 cell-to-cell transmission through virological synapses}
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G.P. McNerney$^1${$^\dagger$}, W. H\"ubner$^2$, D.L. Thompson$^1$, B. Dale$^2$, B. Chen$^2$, and T.R. Huser$^{1,3}$\index{McNerney, G.}\index{H\"ubner, W.} \index{Thompson, D.} \index{Dale, B.} \index{Chen, B.} \index{Huser, Thomas}
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$^1$NSF Center for Biophotonics Science and Technology, UC Davis; $^2$Division of Infectious Diseases, Department of Medicine, Immunology Institute, Mount Sinai School of Medicine, New York, NY; $^3$Department of Internal Medicine, University of California Davis Medical Center, UC Davis

{$^\dagger$}\href{mailto:gmcnhead@ucdavis.edu}{gmcnhead AT ucdavis DOT edu}%$^1${$^\dagger$}, $^1$, $^2$, $^3$,  $^4$, $^4$, $^1$, $^5$, $^{1,2,6}$ 

%G.P. McNerney(1), W. Hübner(2), D.L. Thompson(1), B. Dale(2), B. Chen(2), T.R. Huser(1,3)  (1)NSF Center for Biophotonics Science and Technology, University of California Davis, Sacramento, CA 95817, USA
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\noindent HIV-1 has been shown to be very apt at hiding from the host's immune responses against it.  Of interest here is the highly efficient and evasive cell-to-cell transmission of HIV-1 through the virological synapse (VS) - a cell-cell junction rich in adhesion complexes, virus-associated proteins, and budding viruses.  When a HIV-1 expressing CD4+ T cell finds a susceptible CD4+ T cell, a VS will form and infectious material will be passed off.  Tracking and understanding VS-mediated transmission has thus far been hindered by a lack of suitable probes and assays that do not perturb the virus or transmission.  The first major technical advance here was the development of a fully infectious, natively fluorescent HIV-1 clone termed HIV-1 Gag-iGFP.  This removed the cumbersome requirements of adding exogenous labels or having to infect cells with multiple versions of viral proteins.  To track transmission, we implemented a spinning disk confocal system with a highly sensitive electron-multiplying charged coupled devise camera, fast-timing electronics and acusto-optical tunable filter technology.  Several keen observations were made and quantified as we were able to seamlessly track HIV-1 Gag-iGFP VS-mediate transmission from start to finish.  Throughput, though, remained a serious problem.  Optical tweezers were therefore used to overcome this by intentionally initiating cell-cell contact to form the VS.  This exciting approach is the bedrock of what should become the systematic study of this important HIV-1 transmission mechanism on a case-by-case basis.


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